Wing design typically includes a primary wing surface, or airfoil, having a leading edge and a trailing edge with a control surface located at the leading and trailing edges of the wing. Flaps and ailerons are both examples of control surfaces. Flaps increase wing lift and ailerons allow for roll axis control. The flaps increase wing lift by increasing the camber of the wing. By comparison, ailerons pivot oppositely to increase lift on one wing while reducing lift on the opposite wing to induce a roll. Similarly, elevator sections of the horizontal tail pivotably attach to the fixed tail section to vary lift and provide pitch control. When either the flap or the aileron is activated, the control surface rotates relative to the trailing edge of the wing. Control surfaces are typically rigid structures which maintain their shape throughout rotation. This creates discontinuities or abrupt changes at the hinge area of a conventional control surface. This discontinuity increases the drag and lowers the efficiency of the control surface. Additionally, as the control surfaces are repositioned, discontinuities form between the ends of the hinged control surface and the adjacent portions of the airfoil.
Actuation of control surfaces presents difficult integration issues for advanced airframes. Typical flaps/control surfaces employ traditional actuation schemes that require outside mold line (OML) bumps to accommodate large linear actuators and associated bell cranks. Discontinuities or OML bumps can adversely impact the airflow over the airfoil and control surface. Additionally, these actuation schemes often require large packaging (space) requirements) and cutouts for hinge actuation.